[en] The construction and performance are described of two devices which use the Faraday and Pockels effects, respectively, to obtain smoothly varying transmission functions through radial variation of the beam polarization. Application to beam shaping for lasers of high power with large aperture is mentioned. (U.S.)

[en] A theoretical analysis of third-order nonlinear interactions of focused laser beams is performed for the processes ω₁ + ω₂ + ω₃ → ω₄, ω₁ + ω₂-ω₃ → ω₄, and ω₁-ω₂-ω₃ → ω₄. The total power and far-field beam profile of the generated radiation is related to the total powers of the fundamental beams, to the tightness and location of the focus, and to the value of the difference between the wave vectors of the generated radiation and driving polarization. The optimum degree of wave-vector mismatch as a function of tightness and location of focus is determined for each of the three processes. The process ω₁ + ω₂-ω₃ → ω₄ is found to be unique in that it is always optimized by focusing as tightly as possible. Experimental results, which verify the theory for the processes ω₁ + ω₂ + ω₃ → ω₄ and ω₁ + ω₂-ω₃ → ω₄, are presented. (U.S.)

No abstract available

[en] Here, we investigate the focusing and correcting wavefront aberration of an optical wave using binary amplitude and polarization modulation. Focusing is performed by selectively modulating the field in different zones of the pupil to obtain on-axis constructive interference at a given distance. The conventional Soret zone plate (binary amplitude profile) is expanded to a polarization Soret zone plate with twice the focusing efficiency. Binary pixelated devices that approximate the sinusoidal transmission profile of a Gabor zone plate by spatial dithering are also investigated with amplitude and polarization modulation. Wavefront aberrations are corrected by modulation of the field in the pupil plane to prevent destructive interference in the focal plane of an ideal focusing element. Polarization modulation improves the efficiency obtained by amplitude-only modulation, with a gain that depends on the aberration. Experimental results obtained with Cr-on-glass devices for amplitude modulation and liquid crystal devices operating in the Mauguin condition for polarization modulation are in very good agreement with simulations.

[en] This invention provides a radiation source disposed to direct a beam of radiation through an adjustable beam-limiting device and onto an image receptor located at a selected distance from the source, and automatic means for adjusting the aperture to limit the beam to a cross-sectional size which conforms accurately to the size of the image receptor, at the plane of the receptor. (author)

[en] This paper presents analysis on important issues associated with the design of the refractive laser beam shaping system. The concept of ' singular radius' is introduced along with solutions to minimize its adverse effect on the shaper performance. In addition, the surface boundary constraint is also discussed in details. This study provides useful guidelines against possible general design errors that would degrade the shaper quality or add undesired complication to the system.

[en] This article is a summary of a project undertaken to assess a new multileaf collimator (MLC) for use in the radiotherapy department in the Royal Marsden Hospital. The MLC enables the creation of any shape of radiation beam, without the need to manufacture the customised beam shaping blocks for each treatment field. Assessment of the MLC was therefore required to endorse, or otherwise, that it would provide a more efficient means of beam shaping than the conventional methods. (UK)

[en] This paper presents analysis of important issues associated with the design of refractive laser beam shaping systems. The concept of singular radius is introduced along with solutions to minimize its adverse effect on shaper performance. In addition, the surface boundary constraint is discussed in detail. This study provides useful guidelines to circumvent possible design errors that would degrade the shaper quality or add undesired complication to the system.

[en] The characteristic angle-β concept in electron arc therapy of non-cylindrical target volume is applied in determining the required shape of the arced electron field to yield a uniform dose distribution inside the target volume. The empirical relationships derived for this purpose from the angle-β concept are valid for all field widths and thus offer an improvement over the currently known empirical relationships which were derived as small-field-width approximations. The validity of the determination of field shapes in electron arc therapy with the empirical relationships based on the angle-β concept is confirmed by measurements of dose distributions in a spherical phantom. (Author)

[en] An apodised aperture based on the rotation of plane of polarization producing desirable characteristics on a transmitted light beam such as beam profiling in high flux laser amplifier chains is described. The apodised aperture is made with a lossless element by using one or more polarizers and/or analyzers and magneto-optical Faraday means for selectively rotating the plane of polarized radiation over the cross section to effect the desired apodisation